This invention relates to an apparatus for stacking a zigzag foled web into piles of predetermined height after the web leaves a zigzag folding device. The web is conveyed edge wise to a pile stacking station, and means are provided for directing the folds of the web into a compact stack resting on a support surface of a vertically movable support at the station, the folds being so directed as to lie flat in the stacks being formed without the formation of intervening air cushions.
Known apparatus for the zigzag folding of webs of paper or other materials are normally connected directly to a printing machine, i.e. a printer for the production of forms from webs of indeterminant length. These folding apparatus fold a printed web of paper or other material so that the web can be bent along lines of perforations, disposed crosswise to the direction of travel. In this way a zigzag stack can be formed so that the individual parts of the web between the perforations are superimposed. The folding apparatus may include hoppers which move back and forth for folding the web along the crosslines of perforations into a zigzag stack. The web may comprise one or more superimposed layers of the same or different materials such as thicker or thiner paper. Whether imprinted or not, the zigzag stack will be fed for further processing such as through a high speed printer. During the zigzag folding operation, the web to be stacked is constantly moved back and forth by the folder against the air in its environment. This often leads to undesireable air streams which impede the formation of a flat folded stack particularly for thin and light webs as air is captured and pillows between the folds especially if the web is running at high speed. Moreover, the air bulges or pillowing between the folds may lead to an arched orientation of the stack as the overlying folds shift relative to one another during the folding operation. Thus, it becomes difficult to subsequently form the arched zigzag folded web into squared-off stacks.
U.S. Pat. No. 3,717,335 discloses a cross-web folder for zigzag folding of a web by means of rotating cams. However, since the cams contact surfaces of the folds during web folding, which surfaces may have already been imprinted, the quality of the imprint may be damaged by the rotating cams as by smudging or smearing.
German Pat. GM No. 78 03 900 discloses a web folding device having a conveyor on which the opposed lateral edges of the folded web are supported. Such a device is employed mainly for folding thick and heavy webs and is not adaptable for folding thin and lightweight webs which have a tendency to buldge due to aerodynamic forces.
German Pat. No. 611,694 discloses a folding apparatus for the zigzag folding of webs by means of a movable beater for pressing the folds together. These beaters also contact surfaces of the folds in those locations already imprinted or before printing in a following printing operation. Thus, if already imprinted, the web folds are smudged or smeared by the beaters, and moreover the beaters are incapable of being operated at high speeds (such as approximately 20 Hz) due to their inertia.
German Pat. GM No. 85 09 218 discloses an apparatus for stacking a zigzag folded web into piles including a laterally reciprocating plate 32 which, however, does not avoid or reduce the formation of air pillowing between the folds during stock formation.